Scaling a recipe means that you are adjusting the ingredient quantities for a different amount of servings. While doubling or halving a recipe is relatively easy, you will need to do some math when you want to convert a six-serving recipe for two people or 14 people. Whether you're increasing a recipe or decreasing it—the procedure for adjusting the ingredient quantities is the same.
The first step is to determine a conversion factor; next, you need to multiply this number by the ingredient measurements. If this number is an odd amount for that particular measurement, you will then need to convert to a different type of measurement. This may sound like a lot of work, but you won't need to convert every ingredient in a recipe into another form of measurement. And with these formulas, you are sure to have your recipe turn out perfectly.
Determine the Conversion Factor
The conversion factor is a number you're going to use to convert all the quantities. There's a bit of math involved, but it's OK to use a calculator.
To find your conversion factor, simply divide the desired number of servings by the original number of servings. The resulting number is your conversion factor. Here's the formula:
(desired servings) divided by (original servings) = conversion factor
For example, to scale a 10-serving recipe down to six portions: Divide 6 (desired servings) by 10 (original servings), which gives you a conversion factor of 0.6.
Applying the Conversion Factor
Once you determine the conversion factor, you need to multiply each ingredient measurement by this number. In the example above, you would multiply each ingredient amount by 0.6.
Use this simple example to illustrate the calculations. Say your recipe calls for 2 quarts of chicken stock. All you need to do is multiply 2 quarts by your conversion factor of 0.6:
2 quarts × 0.6 = 1.2 quarts chicken stock
Converting the Measurements to Make Sense
As you see from the example, you are often left with a result that includes a decimal. You are in good luck if it is any of these numbers:
- 0.25: One quarter
- 0.33: One third
- 0.50: One half
- 0.66: Two thirds
- 0.75: Three quarters
When you have other numbers that result, such as the 0.2 of the 1.2 quarters, you can either try to eyeball it or you can make a more precise conversion. The eyeballing route works fine for many types of cooking but can produce a flop if you are baking, where exact measurements are more important.
While the rest of the world uses the metric system, those in the U.S. will need to convert 1.2 quarts into ounces. Consulting a cooking conversion chart, you will learn that there are 32 ounces in a quart, so:
32 × 1.2 = 38.4 ounces
You can round that down to about 38 ounces, but that's still kind of a weird amount. It would be more clear if it were given in cups. Go back to the cooking conversion tool to find that there are 8 ounces in a cup, so:
38 ÷ 8 = 4.75
Which means 1.2 quarts is equal to approximately 4 3/4 cups, a much more doable number.
Don't worry this is going to take a long time or a lot of research. Not every ingredient is going to need multiple conversions. Many will be close to the easier decimals and you can use a half cup, 2/3 cup, or other measures.